The invention relates to a method and simplified device resulting therefrom for measuring a measured object, in particular antenna systems or entire objects into which the antenna systems have been integrated.
Antenna measuring systems are equipped with many devices specific to antenna measurement, some of which are very expensive. Moreover, due to their technical structure and size, the measuring systems are generally not portable. In order to measure a measured object such as, for example, an antenna, these measured objects must therefore always be brought to the measuring system and assembled there. Therefore, spontaneous and rapid on-site measurements of, for example, antennas that are small or have already been installed on satellites or aircraft are hardly possible.
For on-site measurements of an antenna, so-called test caps are commonly used that measure the reproducibility of the field strength of the antenna at a certain position. However, it is not possible to determine the radiation pattern of an antenna using such a test cap.
Moreover, WO 2001/050145 discloses the measurement of an antenna by means of a suspended platform. This platform is primarily provided for large antenna structures. However, the measurement of small antenna structures is difficult to accomplish using platforms of this type.
Exemplary embodiments of the present invention provide a method and a device that allow a more flexible measurement of a radiation field of a measured object such as, for example, an antenna. In particular, the method and device allow the measurement of the electromagnetic field in the direct vicinity of the antenna at any measurement points within a predetermined measurement volume and, using a rapid and precise field transformation, convert the measurement into spatially even and typically equidistant radiation pattern values at a freely selectable distance from the measured object.
These objects are attained by a method in accordance with the features of Claim 1 and a device in accordance with the features of Claim 13. Advantageous developments may be found in the subordinate claims.
Exemplary embodiments of the present invention provide a method by means of which one or more antenna measuring probes are moved within the radiation field, thus recording a number of high-frequency measurement points in any desired spatial distribution. During the movement of each antenna measuring probe, at least one position determination of the respective antenna measuring probe is made simultaneously with or in close temporal proximity to the respective measurement point being recorded in order to assign a position to each measurement point so as to obtain a spatially defined cloud of measurement points. The spatially defined measurement point cloud is then used to produce a radiation pattern for the measured object by means of a field transformation method.
The measurement method is particularly suitable for measuring small and mid-size objects to be measured such as, for example, antennas or diffusing objects, in a cost-effective fashion. The method creates preconditions for antenna or diffusion optimization and is suitable, for example, for troubleshooting by locally diagnosing antenna radiation properties in the course of maintenance and repair work such as, for example, on aircraft and satellites. One advantage of the method lies in the flexibility and low cost for the measurement of the radiation field of a measured object. In particular, using the field transformation method discussed above, the spatial measurement point cloud thus generated may also be used to obtain near-field and far-field radiation patterns of the measured object, which are commonly used in practice, comprising radiation pattern values with an even and typically equidistant spatial distribution.
During the movement of a respective antenna measurement probe, a high-frequency measurement is conducted in order to characterize the respective electromagnetic field components for the purpose of recording an individual measurement point. These measurement points are referred to as high-frequency measurement points.
In the measurement method described here, a special field transformation method is used that, in contrast to existing methods, is able to ascertain antenna radiation patterns from the measurement data clouds mentioned above in a reasonable period of time, at a reasonable cost, and with a sufficient level of precision, at any desired distance from the measured object. This field transformation method is based on a radiation integral calculation that traces the radiation field(s) back to suitable substitute source descriptions such as, for example, even waves or spatial electrical and magnetic current distributions and be able to generate the connection to the measured high-frequency signals via a typically hierarchical, multi-stage translation. Another particular characteristic of this method is the fact that it is able to take into account the influence of a respective antenna measurement probe on the signals to be measured in that each antenna measurement probe is only characterized using its far-field antenna pattern by magnitude and phase. Another characteristic of the field transformation method used here is that it is able to perform the calculation for generating the radiation patterns from “volume data” and not only from surface data. The transformation method used here optionally allows additional suppression of any spatial reflections that may occur.
According to another advantageous embodiment, each antenna measurement probe is provided with a position target, the position of which is detected using measurement technology in order to determine the position of the antenna measurement probe in question. In particular, a measuring laser beam or a measurement arm and/or an inertial measurement system, a geodetic measuring means, or a measurement method based on radio navigation is used to determine the position of the position target.
In the case of curved measurement volumes and/or in order to increase measurement quality, it is also possible for the orientation of the antenna measurement probe to be detected, in particular by expanding the position measurement system accordingly.
It is useful for the movement of a respective antenna measurement probe to be performed manually. Due to the portability of the antenna measuring probe and due to the hand-guided movements, the electromagnetic radiation field of the measured object may be detected in any fashion desired. The position of the measurement points within the measurement volume may be selected in virtually any desired fashion, with the positions always being detected using a highly precise position measurement system so as to be able to determine radiation patterns of the measured object by means of the field transformation method described here from the combination of position and recorded high-frequency measurement point.
According to an additional aspect, the density and distribution of the measurement points in the measurement of the measured object are continuously visualized on an output. When a respective antenna measurement probe is being moved by hand, this allows monitoring of the spaces or area segments in which measurement points have already been recorded and the spaces or area segments in which measurement points must still be recorded
According to another aspect, the number of measurement points recorded is selected in such a way that the density and distribution of the measurement points meet the requirements of the field transformation method, which is based on a rapid radiation integral calculation and takes into account the influence of the measuring probe on the signals to be measured.
It is also useful for spatial reflection to be suppressed when determining the radiation pattern of the measured object. This allows a further improvement in the determination of the radiation pattern of the antenna.
According to another aspect, a respective antenna measurement probe is moved within a measurement volume that surrounds the radiation path of the measured object. Here, depending on the type of antenna, the antenna measurement probe(s) is/are moved within a flat measurement volume in front of the measured object or within an arced measurement volume around the measured object. The later process is particularly selected in the case of antennas having a non-bundling radiation characteristic.
In addition, exemplary embodiments of the present invention involve a device for measuring a radiation field of a measured object, in particular in its immediate vicinity. The device comprises one or more antenna measurement probes which are movable within the radiation field in order to record a number of high-frequency measurement points. It further comprises a position determination means by means of which, during movement of the antenna measurement probe in question, at least one position determination of the respective antenna measuring probe may be made simultaneously with or in close temporal proximity to the respective high-frequency measurement points being recorded in order to assign a position to each measurement point so as to obtain a spatially defined cloud of measurement points. A computation unit is also provided, by means of which at least one distance-dependent radiation pattern of the measured object, for example, near-field and far-field radiation patterns, may be determined from the spatial cloud of measurement points.
The device can also include a frequency-determining means by means of which a high-frequency measurement may be conducted during the movement of the antenna measurement probe for recording a respective measurement point.
According to an additional aspect, a respective antenna measurement probe is provided with a position target whose position may be captured using measurement technology in order to determine the position of the antenna measurement probe. In order to capture the position of the position target, a measuring laser beam, a measurement arm, and/or an inertial measurement system is provided. In principle, it is also possible for other position determination options to be used such as, for example, geodetic measurement means or measurement methods based on radio navigation.
It is useful for a respective antenna measurement probe to be pivotable by hand within the measurement volume, whereby the probe may be moved in a spatially flexible manner due to its portability in order to detect the radiation field, in particular in the direct vicinity of the measured object. Using a suitable field transformation method, it then becomes possible to calculate, for example, near-field and far-field radiation patterns of the measured object or antenna that are distance-dependent.
The invention shall be described in greater detail below with reference to an exemplary embodiment in the drawing.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.